MMP9 and Aortic dissection: Recent studies have demonstrated that matrix metallopeptidase 9 (MMP-9) over-expression is associated with various vascular diseases, including aortic dissection.13 Matrix metallopeptidase 9 is produced from fibroblasts, smooth muscle cells, inflammatory neutrophils, and macrophages in the vessel wall and is thought to play an important role in the onset of aortic dissection.14